The scientists used atomic force microscopy combined with infrared spectroscopy (AFM-IR) to measure the size and map the distribution of oil inclusions inside of microorganism without staining or other special sample preparation. The same method also could help researchers identify other microbes that could be novel potential fuel sources.

The authors led by Ariane Deniset-Besseau from the Laboratoire de Chimie-Physique at the Universite Paris-Sud point out that with the rise in oil prices in recent years, the search has been on for alternative fuels. Though plants such as soy and corn have been popular, the honeymoon ended as people realized how much arable land they were taking up. So now, researchers are seeking additional sources, including bacteria. Streptomyces has become a candidate in this search. It can make and store large amounts of oils called triacylglycerols (TAGs), which are direct precursors of biodiesel. Also, manufacturers already know how to grow vast amounts of it because pharmaceutical companies use the versatile bacterium to produce life-saving antibiotics. To better understand these microbes' potential as a fuel source, Deniset-Besseu's team wanted to explore how Streptomyces stores TAGs.

They used a novel laboratory instrument that combines an atomic force microscope with a tunable infrared laser source. This instrument allows researchers to determine how and where the bacteria store TAGs. Some strains hardly accumulate any oil, whereas others stored large amounts of oil in a way that might be easy to harvest. The researchers conclude that their technique could greatly speed up the identification of other microbes that could produce large amounts of bio-oil.